I had experiences using oil drums to make charcoal. The drums get rusted and become unsafe after 2-3 times of burning (making charcoal). The costs of oil drums and works involved put me back on ‘Thai traditional method’ – digging a hole in the ground, stacking wood for good airflow, putting a (4 inch) ‘metal’ pipe at an angle onto the bottom of the pile for inlet air, and another pipe vertically to the top of the pile for ‘exhaust’, light up the pile and let it burn well then cover the pile with the earth (dug out) well – leaving the inlet and outlet uncovered. Cover both pipes to stop the process. Leave the site for at least 24 hours to cool down.+++Warning: Burns are very painful and difficult to heal. Especially for children!
The art of making good charcoal is in regulating the air flow. Too much air, we get ‘ashes’. Too little air we get half-burnt wood. Types of woods and duration of burn also matter. Practice blocking inlet and observing the result is how magic happens.